Arrangement for repeater stations in electric communication systems



Dec. 28, H. L

ARRANGEMENT FOR REPEATER STATIONS IN ELECTRIC COMMUNICATION SYSTEMS Filed April 7, 1941 'ToRNE).

Patented Dec. 28, 1943 UNITED STATES PATENT OFFICE ARRANGEMENT FOR REPEATER- STATIONS IN ELECTRIC COMMUNICATION SYSTEMS John Henry Mole, Eastcote, Ruislip, England, assignor to Siemens Brothers 8: Co. Limited, Westminster, London, England, a British com- Application April 7, 1941 Serial No. 387,236 In- Great Britain September 15, 1939 1 Claim. (CL 178-63) from one of the distant attended stations by imposing these potentials on the cable conductors which carry the signal currents. These potentials can be supplied by applying to the cable conductors a direct current, the anode potential for the valves being tapped off a resistance in the circuit of the cathode heaters. This method only requires the use of simple filtering arrangements, but to'obtain a suitable anode voltage in conjunction with a small heater current the values of the resistance required in the heater circuit necessitates the dissipation of an undesirable amount of heat. Such a disadvantage can be overcome if alternating current, rectified for the supply of anode potential is used, but a difficulty is then likely to be met in providing filtering arrangements toprevent the harmonics of such supply interfering with the communication circuits.

It is the object of the invention to provide arrangements which overcome these difliculties.

According to the present invention direct current is fed to the amplifier at an unattended repeater situated between two attended stations from each attended station, the cathode heating current being fed from one of the attended stations and the higher voltage anode current from the other. In this way considerable heat dissipation from a resistance in the cathode heater circuit is avoided and the filtering arrangements remain simple. Interference from harmonics which is liable to occur with rectified alternating current is also avoided. Arrangements may also be provided whereby the repeater may be cut out of circuit and a through connection made to facilitate operations such as testing.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing.

The drawing shows in diagrammatic manner the arrangements at an unattended repeater station and the adjacent ends of two cables connecting the repeater to the two attended stations.

The cables are shown as CAB and CBC, respectively. ,Cable CAB connects the'repeater R,

at the unattended station B, to the attended station A. Cable CBCconnects the repeater to the other attended station C.

The repeater apparatus, shown as R enclosed in a triangle, may take any suitable form. The direction of transmission through the repeater is shown by the arrow head of the triangle; IT and CT are the imput and output transformers, respectively, by means of which the repeater is operatively coupled'to the adjacent cable sections.

The primary of the transformer IT is connected at one end to the central conductor of cable CBC as by a wire In, in the length of which I or thermionic valve of the repeater and wire l2.

The primary of transformer OT is connected between the anode P of the vacuum tube and the wire l2, as by a wire M inthe length of which is a condenser l5. One end of the secondary of the transformer OT is connected to the central conductor of cable CAB as by a wire [6' in the length of which is a condenser C and a blocking condenser CO. The other end of the secondary of the transformer OT is connected to the outer or return conductor of cable CAB as by a wire I! and wire I2.

Low tension direct current for heating the cathode K of the tube of the repeater R is supplied over the cable CBC from station C, and the high tension direct current for the anode P is supplied over cable CAB from station A. The currents are fed over the central conductors, the outer conductors forming return paths. Thus, connection is made from cable CBC to terminal LT, to which the cathode or cathode heaters are connected, as by the wire In, and a wire l8 in th length of which is a suitable choke CK. Connection is made to terminal HT, to which the anode is connected by wire I4 and a wire 20, as by the wires 2|, 22 and the wire l6.

In the embodiment illustrated, there is included other apparatus, in particular, a relay A which permits the repeater to be bridged when the power supply to the repeater is cut off, the contacts al, a2 and a3 being shown as spaced apart for the sake of convenience. The contacts are shown in the position they occupy when the winding of the relay is not energized, or, as stated hereinafter, when the relay is unoperated.

When the relay is in its unoperated position, it will be seen that the central conductors of both cables CBC and CAB are directly connected together, as by wires I 0, l8, I9, 23 and Hi. The outer conductors of both cables are also directly connected together, as by wire l2. The repeater is thus out of circuit and a through connection between the two cables exists over which communication can take place under emergency conditions such as the failure of the power supply to the repeater.

To supply power to the repeater, the high tension anode current is switched on at station A and a circuit is closed which will extend from the source of high tension anode current at station A, over the central conductor of cable CAB, wire 16, condenser C, contact al in its unoperated position, relay A, wire I2, the outer conductor of cable CAB, to the source of current. The initial rush of current will flow over this circuit, and relay A will operate on the charging current of condenser C to energize relay to connect itself directly to the central conductor of cable CAB over contact al in its operated position, and will remain energized over the cable CAB.

The high tension current fed over cable CAB will now be fed to the terminal HT through a wire 24, and Wire 2|, thence to the anode P, through wires I4 and 20, the return path being through the tube to the cathode and wire I2, the anode current return path being over the outer conductor of cable CAB. Contact a2 disconnects the through metallic circuit between the central conductors of the two cables by changing from its unoperated to its operated position, and in the latter position, connects to central conductor of cable CBC over the choke CK to the low tension cathode terminal LT. Current from the low tension source of cathode heating current at station B will flow over the central conductor of cable CBC, wires and I 8, contact a2 in its operated position, over choke CK, terminal LT and thence to the cathode, finding a return path over wire l2, the outer conductor of cable CBC and the current source.

The function of the choke CK is to separate the low tension cathode heating current from the alternating signaling currents.

In order to reduce the instability of the amplifier due to the presence of the relay contacts and their wiring, two relays may be employed, one situated at one end of the repeater and controlling contacts al and a3, and the other situated at the other end of the repeater and controlling contact a2, the windings of the relays being connected in series. The effect of capacity coupling through the relay contacts is further minimized by the earth over contact a3.

Whilst arrangements have been described in which the controlling factor is the high tension current it will be appreciated that it is possible for this control to be exercised by the low tension current. For example the low tension current may be fed from station A and the high tension from station C, and in this example the terminal designated HT would form the cathode terminal and be connected to the cathode K and the terminal designated LT would form the anode terminal and be connected to the anode P. The capacity of the condenser C would be suitable ,for use with the low tension supply and relay A would be designed accordingly.

It will be appreciated that with the arrangements described no losses due to useless dissipation of energy in the repeater occur and the arrangements for separating the power and signaling currents are simple.

What is claimed is:

An electric communication system comprising a transmission circuit, an unattended repeater station intermediate between two terminal ends of said transmission circuit thereby separating the transmission circuit into two parts, said repeater station comprising thermionic valve ampliiying equipment including cathode and anode terminals, means associated with said transmission circuit at said repeater station for metallically connecting only the said cathode terminals to one of said two parts of the transmission circuit, and means associated with said transmission circuit at said repeater station for metallically connecting only the said anode terminals to the other of said two parts of the transmission circuit, said means operating consequent on the application of potential at a terminal end to the one of the said two parts connected thereto for effecting the respective connections of said cathode and anode terminals.

JOHN HENRY MOLE. 

